1. Field of the Invention
This invention relates to a data carrier, in particular a bank note, paper of value, identity card or the like, having a security element disposed on the surface thereof.
2. Background of the Invention
For protecting data carriers, in particular security documents, manufacturers provide these documents with additional security elements intended to authenticate them, on one hand, and to serve as protection from unauthorized reproduction of the data carrier, on the other hand. Along with a number of elements which have been produced by separate printing or other production processes, the use of optically variable elements which are applied to such data carriers have become widespread.
For detecting the authenticity of a document having a security element in the form of a reflection hologram consisting of an embossed layer of lacquer and a reflecting metal layer, it has been proposed for example in WO 94/11203 to use an adhesive layer with a fluorescent substance for applying the optical security element to the document. For detecting the authenticity of the document this fluorescent substance can be transferred to the document together with the optical security feature. However the fluorescent substance is only visible if openings are provided in the metal layer of the element so that the fluorescent substance is visible through the openings. Alternatively it has been proposed in WO 94/11203 that the document material be transparent so that the adhesive layer bearing the fluorescent substance is visible from the side facing away from the optical security element.
A disadvantage of the fluorescent adhesive known from WO 94/11203 is that it can only be applied in documents or optical security elements which fulfill special boundary conditions suitable for the adhesive. Specifically, the document material must either be transparent or the optical security element to be used must provide a view of the subjacent, fluorescent adhesive layer at least in partial areas. Another disadvantage is that the element could be detached and glued to a falsified document without this abuse being recognizable, since part of the fluorescent adhesive layer would still adhere to the element after its detachment and thus still provide a qualitatively correct authenticity signal, although it is quantitatively too small due to a lower fluorescence intensity. When authenticity elements are quickly tested, only the qualitative properties are usually evaluated, such as the presence of fluorescence or its wavelength, so that insufficient intensity of the signal does not enter into the detection of whether or not a document is authentic.
The problem to be solved is to provide a document with a security element wherein the security element on the document can be protected effectively without the document or security element having to meet special requirements of the type described.